1. Field of the Invention
The present invention relates to a three-dimensional display device, and in particular, to an autostereoscopic three-dimensional display device using a parallax barrier.
2. Description of the Related Art
A three-dimensional display device may be categorized as a stereoscopic display device where a user wears viewing aids such as polarizing glasses, or an autostereoscopic display device where the user can see a desired three-dimensional image without wearing such viewing aids.
A common autostereoscopic display device utilizes an optical separation element, such as a lenticular lens, a parallax barrier, or a microlens array, to spatially separate or isolate the left-eye image part and the right-eye image part displayed at an image display unit in the directions of the left and right eyes of the user, respectively.
In particular, the parallax barrier may be formed with a liquid crystal shutter utilizing a transmission type liquid crystal display, and in this case, it may be converted between a two-dimensional mode and a three-dimensional mode. Thus the parallax barrier can be applied to laptop computers or cellular phones.
Generally, the parallax barrier includes stripe-shaped light interception portions and light transmission portions. It selectively separates left and right eye images displayed at the image display unit through the light transmission portions such that the left and right eye images are respectively provided to the left and right eyes of the user.
A common three-dimensional display device having a parallax barrier displays left and right eye images according to left and right image signals inputted to pixels of the image display portion, and it separates the left and right eye images spatially by using the parallax barrier.
However, since the left and right images are entered into the respective eyes of the user, the resolution of a three-dimensional image is no more than half as fine as that of a two-dimensional image.
To solve this problem, a time-sharing type of three-dimensional display device has been developed.
An image display portion of the time-sharing type of three-dimensional display device shows patterns of left and right eye images, and the patterns of the left and right eye images are changed alternately at a given frequency. Patterns of the light interception portions and the light transmission portions of the parallax barrier are changed alternately at the given frequency.
Consequently, the time-sharing type of three-dimensional display device provides a three-dimensional image having a resolution as fine as that of a two-dimensional image.
The parallax barrier of the time-sharing type three-dimensional display device may be formed with a liquid crystal shutter utilizing a transmission type of liquid crystal display, and the liquid crystal display may include first electrodes and second electrodes formed in a striped pattern and arranged alternately and repeatedly relative to each other.
Accordingly, the first electrodes and the second electrodes of the liquid crystal display are arranged corresponding to an image for the left eye and an image for the right eye displayed by the image display portion. A driving voltage is applied alternately and repeatedly to the first electrodes and to the second electrodes during operation of the image display portion.
Light transmittance rates of portions of the parallax barrier corresponding to each of the electrodes should be uniform to enable the user to see images having a uniform brightness during the operation of the image display portion.
However, it is difficult for the time-sharing type of three-dimensional display device to maintain a uniform light transmittance rate due to differing lengths of electrode paths along which applied voltages are conducted.